.TITLE MF08..	SET FDB POINTER TO CORRECT FDB CONTROLED BY F$LUN
	.IDENT /MF08../
;
;
F$SWITCH::			;SET UP FDB POINTER
;
;		ENTRY CONDITIONS
;		F$LUN	SET UP
;
;		EXIT CONDITIONS
;		NONE
;
	SAVE R3			;PROTECT R3
	MOV F$LUN,R3		;HOLD LUN NUMBER
	BLE	10$		;J IF INVALID VALUE
	DEC R3			;CORRECT FOR OFFSET FDBS COUNT FROM ZERO
	MUL #F.FDB,R3		;SET UP OFFSET
	ADD #F$FDBS,R3		;GET ABSOLUTE ADDRESS
	MOV R3,F$FDB		;HOLD FDB ADDRESS
10$:	UNSAVE R3		;RESTORE USED REGISTER
	RETURN			;BACK TO CALLING PROGRAM
;
;
;
	.END
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